CRAGs: Andy Ross (2nd l.), leads a march of British Carbon Reduction Action Groups (CRAGs), a network of people voluntarily cutting their carbon footprint to demonstrate the public's desire for action on climate change.

London — It's the time of year when many Britons might be thinking of hopping on a plane to get some sun. But Andy Ross won't be joining them.

It's not that Mr. Ross is scared of flying. Instead, he is trying to make the world a cooler place. By cutting out leisure flights and adopting a host of other measures, he has reduced his own carbon emissions by more than 80 percent in two years.

More important, Ross has not been acting alone. Determined to make a difference, he has pioneered a movement of scores of Britons who are voluntarily rationing their energy usage to limit their carbon footprint.

Carbon rationing action groups, or CRAGs, are proliferating across the country (www.carbonrationing.org.uk) and have recently spread to the United States and Canada. Ross reckons there are about 16 up and running in Britain and a similar number in formation. Each has up to a dozen members who meet regularly to swap tips, set targets, and agree to rules on how to shrink their carbon footprints.

"It's empowering," says Ross, "because it makes you feel like you're doing something rather than sitting on the side carping about it."

So how do CRAGs work? The idea is that everyone in the group voluntarily adheres to a carbon ration. Members supply the group's "carbon accountant" with details of their car mileage, household bills, and any personal air travel. This is then converted into CO2 emitted using simple online conversion tools.

Most of the British groups are taking, as a point of reference, an average CO2 emission for 2005 of about 5 metric tons (or 5.5 tons – roughly comprising 2.5 metric tons on home energy use, 1.5 metric tons on flying, and 1 metric ton on driving). Some are reducing their emissions by 10 percent each year. And some have set up a system of fines such that "overemitters" must pay about 4 pence (8 cents) for every kilo over ration that they emit.

Cheap? Not at all. In the Islington CRAG in North London, Doug Angus flew to South America and had to pay around Â£200 (about $400) as a result. The same thing happened in Ross's group. The money is either divided up among other members or donated to green causes.

Skeptics point out that there are too few craggers currently to make a difference. But craggers themselves say their action is an important demonstration of public will. Scientists are calling for an 80-percent cut in greenhouse-gas emissions by 2050 to stop the world from overheating, but many governments are lagging behind the curve, fearful that the public is not ready for austerity measures.

CRAGs "make it much harder for governments to say people would never accept carbon rationing," says George Monbiot, a prominent British environmental campaigner whose 2005 speech calling for a "riot of austerity" inspired Ross to pursue the idea.

"If people are doing it voluntarily, then it really puts the government on the defensive," Mr. Monbiot adds.

CRAGs also provide a forum for members to swap tips about carbon-reduction measures. Aside from the obvious (turning down the thermostat, switching off appliances at the wall, and fitting energy-saving light bulbs), craggers swear by insulation, new efficient boilers, and solar panels for heating water. Many have given up flying, and some have sold their cars.

"I'm getting my windows replaced, I've replaced the fridge because it was a major consumer of electricity, and I'm switching to a laptop because it saves 80 percent of the energy" used for a desktop, says John Ackers of the Islington CRAG. "I'm putting on more clothes during the winter as well."

Shannon Moore, who set up one of the first American CRAGs in Maryland, says that her craggers have taken to public transport, car-sharing, drying racks, insulation, reduced driving, and properly inflated tires. "The group is coming up with new ideas all the time about how the average person can cut their carbon emissions," she says.

Significantly, the 40 Maryland craggers have a target this year of just under 11,000 kilograms (about 12 tons) – more than double that of their British counterparts.

Ross is now considering taking things one step further by moving from his one-bedroom Glasgow flat to sharing with friends. Cohabitants get a full carbon ration, so emissions are divided up.

Everyone, it seems, is pulling on extra layers. "We wear more jumpers," says Angela Raffle of the Bristol CRAG. "It's not a hardship compared to what will happen if we don't do something." Anna Plodowski, from south London, doesn't even have central heating. Not that it seems to bother her daughter. "She can play for hours wearing next to nothing, and I'm wearing all these jumpers [sweaters]. She feels it much less than I do."

The impression one gets, even after a mild winter, is of hardy types huddling in their sweaters while the vast majority just turn up the thermostat a few notches. And herein lurks a problem with CRAGs. The danger of such voluntarism can be that the selfless merely create ecological space for others to fill.

As Monbiot puts it, "you can give up your car, but unless there's a government policy to make sense of that decision, all you might be doing is creating space on the road for someone to drive a less efficient car than you were."

Ms. Plodowski sees it slightly differently. She believes that because CRAGs ensure that everyone is treated fairly, they deal with a problem at the heart of the climate crisis: that people are reluctant to act because they think others will spoil their efforts by not joining in.

"CRAGs can go mainstream," she says, "because ideas of fairness are important to human behavior."

Already, CRAG leaders say their groups are reaching out well beyond the core constituency of the "green ghetto." Ms. Raffle says her group consists of engineers, teachers, doctors, and retirees. "We are the opposite of your stereotypical environmentalists," she says.

But Ross, the cragger pioneer, is unsure whether CRAGs will appeal to everyone. "It's very difficult to expect people to do something voluntarily which is so countercultural," he says regretfully.